It is well-known that hydrogen is a very efficient and clean-burning fuel. Hydrogen can be combined with oxygen through combustion, or through fuel cell mediated oxidation/reduction reactions, to, produce heat, or electrical power. The primary product of this reaction is water, which is non-polluting and can be recycled to regenerate hydrogen and oxygen.
Currently, hydrogen energetics is the focus of interest in nuclear industry, motor transport, auto industry, chemical industry, aerospace industry, portable power sources industry (cellular phones, computers, home appliances), etc. In particular, the transport sector is a consumer of about half of the world's crude oil production. Therefore, this sector of the economy is intensively adopting the use of hydrogen fuel. This would solve environmental problems, especially in large megapolises and industrial regions.
One of the problems of hydrogen energetics is safe storage and delivery of hydrogen fuel to a combustion -cell. Most generally, hydrogen is stored either in liquid form or as a gas under pressure in a large vessel. Liquid storage systems require significant insulation so that the liquid state can be maintained while gas storage systems require large and heavy vessels.
Existing accumulation techniques with compressed gaseous hydrogen in tanks provide a relatively low hydrogen weight content (the ratio of the weight of hydrogen in accumulator to the weight of accumulator), i.e., up to 10 weight %, and there are certain restrictions for further growth of this parameter along with low explosion protection. Hydrogen can be stored as a liquid, if cooled down to −253° C. (up to 7.1 weight %). However, about one third of hydrogen energy (11 kW•hour/kg H2) is consumed to reach this temperature, while hydrogen evaporation losses can reach 3-5% daily.
For example, hydrogen accumulators and hydrogen accumulation methods based on solid bonding of hydrogen (e.g., in metal hydrides or sorption on dispersed nanomaterials) are known in the art (see, for example, Russian Federation Pat. Nos. 2037737 and 2038525). These hydrogen accumulation and storage devices are relatively explosion-proof, because hydrogen features no excess pressure. However, these techniques are inertial, and it takes time for them to start working (several minutes). Moreover, hydrogen absorption and release consume a lot of heat. Likewise, weight content of hydrogen is rather low (about 4.5%). Weight content is a function of the volume of hydrogen in accumulating agent, and specific weight of the accumulating agent.
A hydrogen storage tank is described in Russian Federation Pat. No. 2222749 that includes a sealed housing that accommodates an internal liquefied hydrogen storage vessel, and a gas filling system allowing lower hydrogen losses and filing duration. This tank is made of relatively light heavy-duty composite materials. According to estimation, such a tank can store about 3.2 kg of hydrogen, and the weight hydrogen content is therefore equal to 8%. The main drawbacks of this tank are related to explosion hazards, relatively low hydrogen content per vessel volume unit, and gas losses due to-gas release from the tank.
U.S. Pat. No. 4,328,768 describes a fuel storage and delivery system wherein hollow microspheres filled with hydrogen gas are stored in a fuel storage chamber at pressures of 400 atm from which the microspheres are directed through a heated delivery chamber wherein hydrogen gas is freed by diffusion and delivered to an engine, after which the substantially emptied microspheres are delivered to a second storage chamber. The substantially emptied microspheres are removed by mechanical means, such as a pump, to a storage chamber from which they can be removed for refilling.
A hydrogen accumulation in hollow 5-200 μm glass microspheres with 0.5-5 μm walls is described by S. P. Malyshenko and O. V. Nazarova. (see a paper titled: “Hydrogen Accumulation” published in <<Nuclear and hydrogen energetics and technology>> (in Russian), issue 8, PP. 155-205, 1988). When under pressure at 200° C.-400° C., hydrogen diffuses intensely through the walls, fills in the microspheres and remains there under pressure after cooling. When heating the microspheres to the above temperatures at ambient hydrogen pressure of 500 atm, hydrogen weight content in the microspheres reaches 5.5%-6.0%. The hydrogen weight content can be even lower, if the ambient hydrogen pressure is lower. On heating to 200° C., about 55% of hydrogen contained in microspheres will be released. Accordingly, about 75% of hydrogen contained in microspheres will be released on heating to 250° C. At hydrogen storage in glass microspheres, its wall diffusion losses are about 0.5% per 24 hours. In the case when the microspheres are coated with metal films, diffusion losses of hydrogen at room temperatures can be 10 to 100 times lower. The main drawback of this method is in the fact that the microspheric accumulator cannot be charged at very high hydrogen pressures and high temperatures, because it makes the process hazardous due to the low tensile strength of glass, which is within 20 kg/mm2. This does not allow hydrogen weight content in the microspheres to be substantially higher than 6% (by weight).